/* pages.css — 页面系统样式 */
    /* ════════════════════════════════════════
       页面系统样式
    ════════════════════════════════════════ */

    .app-page {
      display: none;
      min-height: 100vh;
    }

    .app-page.active {
      display: block;
    }

    .back-btn {
      position: fixed;
      top: 20px;
      left: 20px;
      z-index: 100;
      padding: 12px 20px;
      background: rgba(255, 255, 255, 0.95);
      border: none;
      border-radius: 24px;
      font-size: 0.95rem;
      font-weight: bold;
      color: #667eea;
      cursor: pointer;
      box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
      transition: all 0.3s ease;
    }

    .back-btn:hover {
      transform: translateX(-4px);
      box-shadow: 0 6px 16px rgba(0, 0, 0, 0.15);
    }

    .sub-page-container {
      max-width: 720px;
      margin: 0 auto;
      padding: 80px 24px 100px;
    }

    .sub-page-header {
      margin-bottom: 24px;
    }

    .sub-page-header h2 {
      font-size: 1.5rem;
      color: #333;
      margin: 0;
    }

    .sub-page-content {
      background: #fff;
      border-radius: 16px;
      padding: 24px;
      box-shadow: 0 4px 16px rgba(0, 0, 0, 0.08);
    }


    /* 移动端适配 */
    @media (max-width: 480px) {
      .sub-page-container { padding: 70px 16px 80px; }
      .sub-page-content { padding: 16px; }
    }